I carry a reasonable FAK with me all the time. It is limited to the things that I know how to use for obvious reasons. Although it is more than usually equipped with meds.

My question though is for any paramedics, EMT, WEMT, medics etc out there. If I had the space what small pieces of equipment would it be useful for someone to have at the scene of an incident which someone trained in their use would find invaluable but may not always have with them (off duty). I am thinking strictly about instances where actual medical aid may not be immediately forthcoming e.g train wreck in a tunnel, area sealed off due to terrorist use of dirty bomb, trapped inside collapsed building etc. Depending on the usefullness/weight ratio I may well be willing to carry a bunch of extra stuff in case someone at the scene can use it - so any suggestions as to stuff you would like me to provide?